Beaufort Scale

Courtesy Wikipedia!

Beaufort number Description Wind speed Wave height Sea conditions Land conditions
0 Calm < 1 km/h 0 m Flat. Calm. Smoke rises vertically.
< 1 mph
< 1 knot 0 ft
< 0.3 m/s
1 Light air 1.1–5.5 km/h 0–0.2 m Ripples without crests. Smoke drift indicates wind direction. Leaves and wind vanes are stationary.
1–3 mph
1–3 knot 0–1 ft
0.3–1.5 m/s
2 Light breeze 5.6–11 km/h 0.2–0.5 m Small wavelets. Crests of glassy appearance, not breaking Wind felt on exposed skin. Leaves rustle. Wind vanes begin to move.
4–7 mph
4–6 knot 1–2 ft
1.6–3.4 m/s
3 Gentle breeze 12–19 km/h 0.5–1 m Large wavelets. Crests begin to break; scattered whitecaps Leaves and small twigs constantly moving, light flags extended.
8–12 mph
7–10 knot 2–3.5 ft
3.5–5.4 m/s
4 Moderate breeze 20–28 km/h 1–2 m Small waves with breaking crests. Fairly frequent whitecaps. Dust and loose paper raised. Small branches begin to move.
13–17 mph
11–16 knot 3.5–6 ft
5.5–7.9 m/s
5 Fresh breeze 29–38 km/h 2–3 m Moderate waves of some length. Many whitecaps. Small amounts of spray. Branches of a moderate size move. Small trees in leaf begin to sway.
18–24 mph
17–21 knot 6–9 ft
8.0–10.7 m/s
6 Strong breeze 39–49 km/h 3–4 m Long waves begin to form. White foam crests are very frequent. Some airborne spray is present. Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic bins tip over.
25–30 mph
22–27 knot 9–13 ft
10.8–13.8 m/s
7 High wind,
moderate gale,
near gale
50–61 km/h 4–5.5 m Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray. Whole trees in motion. Effort needed to walk against the wind.
31–38 mph
28–33 knot 13–19 ft
13.9–17.1 m/s
8 Gale,
fresh gale
62–74 km/h 5.5–7.5 m Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray. Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded.
39–46 mph
34–40 knot 18–25 ft
17.2–20.7 m/s
9 Strong gale 75–88 km/h 7–10 m High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility. Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over.
47–54 mph
41–47 knot 23–32 ft
20.8–24.4 m/s
10 Storm,[7]
whole gale
89–102 km/h 9–12.5 m Very high waves with overhanging crests. Large patches of foam from wave crests give the sea a white appearance. Considerable tumbling of waves with heavy impact. Large amounts of airborne spray reduce visibility. Trees are broken off or uprooted, structural damage likely.
55–63 mph
48–55 knot 29–41 ft
24.5–28.4 m/s
11 Violent storm 103–117 km/h 11.5–16 m Exceptionally high waves. Very large patches of foam, driven before the wind, cover much of the sea surface. Very large amounts of airborne spray severely reduce visibility. Widespread vegetation and structural damage likely.
64–73 mph
56–63 knot 37–52 ft
28.5–32.6 m/s
12 Hurricane force [7] ≥ 118 km/h ≥ 14 m Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility. Severe widespread damage to vegetation and structures. Debris and unsecured objects are hurled about.

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